The present invention is concerned with a method for the measurement of properties of a liquid present in a vessel, for example for the measurement of the absorbance of a liquid, of the properties of an agglutination, precipitate or any other reaction result placed on the bottom of a vessel, by means of radiation and of a detector receiving radiation while the vessel moves along with a rotor revolving around the vertical axis of a centrifuge, the beam of measurement coming from the source of radiation passing substantially horizontally and the intensity of the radiation passing through, or reflected from, the contents of the vessel being measured. The invention is also concerned with an apparatus for the implementation of the method, which apparatus comprises a rotor revolving around a vertical axis, to which rotor the vessel can be fitted, one or several detectors receiving radiation and fitted so that the beam of measurement received by the detector(s) passes substantially horizontally, as well as an output unit.
Various tests based on agglutinations are in common use, blood-group identifications, antibody determinations, and rheumatic-factor measurements. In blood-group analytics and in antibody determinations the agglutination of red blood cells is concerned. The rheumatic factor is commonly measured by means of the agglutination of latex particles.
It has been customary to read the results of agglutination reactions visually. An experienced reader is also quite skilful in distinguishing between agglutination and non-agglutination. Such a mode of output is, however, quite subjective, and this is why the result is not always completely reliable. In clear situations with strong agglutination, visual reading is certainly no problem, but weak reactions of agglutination are often problematic. Among agglutination reactions, most difficult to interpret is a weak Rh-positive result obtained in blood-group identifications. In such situations it is of essential importance to obtain a reliable output, because the safety of the patient is concerned.